The present invention relates to a forceps specially designed for inserting an endotracheal tube into the trachea of a patient through the crico-thyroid membrane.
It is important during emergency care to keep the patient's airway open. In fact, emergency care providers are trained to place attention on the Airway first, before Breathing and Circulation (the so-called ABC's of emergency care). The airway is easily obstructed. Anything from the patient's own tongue, blood, vomitus or small bits of food can occlude the airway, interrupting the flow of air into and out of the lungs. Failure to provide adequate oxygen to the lungs, and ultimately to the brain, can result in hypoxia, which can rapidly progress to anoxia and death. The most common technique in the emergency setting for securing the airway is to place an endotracheal tube into the trachea of the patient through the mouth. In some instances, the endotracheal tube can be inserted into the trachea through the nasal passages via the nasal-tracheal route. Sometimes oral or nasal introduction of the endotracheal tube is either not possible or is contra-indicated. For example, if the patient's jaw is clenched shut, one cannot use the oral-tracheal route. Blood flowing from the nose could be an indication of a basilar skull fracture, thus contra-indicating the nasal-tracheal route. At the scene of an accident, paramedics sometimes find patients with clenched jaws from a closed head injury or with blood flowing from the nose from a skull fracture. Inadequate respiration must be resolved in those instances by a surgical intervention through the crico-thyroid membrane.
As shown in FIG. 1, the crico-thyroid membrane (16) is a transverse oval-shaped membrane located below the thyroid cartilage (12) and above the cricoid cartilage (14) in the throat just below the prominence commonly known as the Adam's Apple (15).
The thyroid (derived from the Greek word for "shield") is the largest cartilage in the larynx and is shown in FIG. 2. It consists of two lateral walls (17, 19) united at an acute angle in front forming a vertical projection in the middle line which is prominence above and called the Adam's Apple (15). Each side is quadrilateral in form. The upper border (21) of the thyroid cartilage (12) is sinuously curved and is concave on the posterior part (23). The lower border of the thyroid cartilage (12) is nearly straight in front. This lower border of the thyroid cartilage (12) is connected to the cricoid cartilage (14) in and near the median line by the middle portion of the crico-thyroid membrane (16) and, on each side, by the crico-thyroid muscle (not shown). The cricoid cartilage (14) (derived from the Greek work for "ring" because it resembles a signet ring) is smaller, but thicker and stronger than thyroid cartilage (12) and forms the lower and back part of the cavity of the larynx. It consists of two parts: a quadrate portion (24) situated to the rear and a narrow ring anterior portion (23) or arch about 1/4 or 1/5 the depth of the posterior part, situated in front, thus, the appearance of a signet ring. The quadrate portion (24) rapidly narrows at the sides of the cartilage into the anterior portion (23). The anterior portion (23) is narrow and convex and affords attachment externally in front and at the sides of the crico-thyroid muscle (not shown). The lower border of the cricoid cartilage (14) is horizontal and connected to the upper ring of the trachea (18) by fibrous membrane. The upper border of cricoid cartilage (14) is directed obliquely upward and backward owing to the greater depth of the posterior surface. It gives attachment in front through the middle portion of the crico-thyroid membrane (16), at the sides to the lateral portion of the same membrane. The crico-thyroid membrane (16), thus, extends between the lower margin of the thyroid cartilage (12) and the upper margin of the cricoid cartilage (14). It is convex, concealed on each side by the crico-thyroid muscle, but subcutaneous in the middle line. It can accommodate endotracheal access through the tough cartilage below the vocal cords and at the entry way to the trachea (18).
In the hospital setting, surgeons use advanced tools to perform a surgical cricothyrotomy or they use the more difficult and technically advanced tracheotomy procedure. At the scene of an emergency, like a motor vehicle accident, paramedics do not have at their disposal the equipment that is available in the hospital setting. The only tool available to the paramedic is a scalpel to make the incision laterally across the crico-thyroid membrane. The fifth digit is used for blunt dissection prior to inspection of the endotracheal tube (22).
An endotracheal tube (22) is a curved, bendable plastic tube of a prescribed internal diameter varying usually from 3 to 9.5 mm and with a bias cut distal end (25). The tube (22) is introduced into the trachea (18) through a 10 mm incision (67) in the crico-thyroid membrane (16). The incision is made across the crico-thyroid membrane (16) transverse to the long axis of the neck of the patient. It can be very difficult to advance the tube (22) down trachea (18) since it is being introduced at a 90-degree angle through the incision with only a millimeter or two to spare. Paramedics frequently find that they have to make a larger incision in order to turn the endotracheal tube down the longitudinal axis of the trachea (18) or the paramedic must slowly advance the tube (22) into the trachea (18) by using the fifth digit to bend the distal end of the tube (22) in order to navigate the 90-degree angle, thus, wasting valuable time and executing an extremely difficult digital maneuver. When one considers the confusion that can exist at an emergency scene, one can easily see that it would be extremely helpful to have a device specially designed for use in the field to perform a surgical crico-thyrotomy more easily without resorting to the surgeon's tray full of instruments.
Standard endotracheal tubes designed for oral entry are longer than is necessary for a crico-thyroid membrane entry. When they are used in a crico-thyrotomy, the proximal end of the tube sticks out too far from the incision and can get in the way or even be hit by the attending personnel causing additional damage to adjacent structures.
The description of the anatomy was taken from Gray's Anatomy 1977, Crown Publishers, Inc., Library of Congress Catalog No. 76-52804, pp. 955-965.